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Fossilised crustacean boasts oldest penis

The well-endowed fossilised creature has organs (circled) strikingly similar to modern ostracods (Image&colon;

By Maggie McKee

A newly discovered 425 million-year-old fossil boasts a lurid claim to fame – it has the oldest penis on record.

The five millimetre long crustacean, discovered by UK and US researchers, has been named Colymbosathon ecplecticos – derived from the Greek for “astounding swimmer with a large penis”.

The well-endowed creature is surprisingly similar to modern relatives, despite being entombed nearly half a billion years ago, says the team.

David Siveter, a paleontologist at the University of Leicester, and colleagues unearthed the clamlike species in a rock formation in Herefordshire, UK. The creature possesses a hard shell, an organ for grabbing prey, six gills, as well as a “copulatory organ [that] is large and stout”, says the team.

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The newly discovered fossil belongs to a subclass of crustaceans known as ostracods. These are among the most abundant fossils on Earth as they are more easily preserved than softer animals because of their hard shells. They are also plentiful with 33,000 ostracod species found throughout history. The oldest fossilised ostracod shell is about 500 million years old.

However, this latest find is unprecedented in that the fossil has preserved not just the shell but the shape of the creature’s soft tissue – a lucky result of environmental conditions 425 million years ago.

Volcanic eruption

The virile crustacean was preserved by ash from a volcanic eruption swirling to the bottom of a sea that submerged western England 425 million years ago.

The ash hardened quickly around the tiny aquatic victims, forming a mould of each curve and limb before their bodies decayed. The resulting nodules around the fossils resemble potatoes that can be dug up easily from the surrounding rock known as the Herefordshire Lagerstätte.

To free the fossils for study, the researchers used a technique they developed a few years ago to crack open the nodules and shave off layers just 20 millionths of a metre thick. Each layer is then photographed. A computer program then assembled the photos into a 3-D ‘virtual’ fossil.

The method revealed long extremities probably used for swimming, a pair of compound eyes, as well as the creature’s big phallus.

Now-extinct family

Siveter says he scoured museums for examples of similar, modern organisms and found them in a family called Cylindroleberididae.

“It’s very exciting to get an animal that looks so modern but dates back 425 million years, and never at this age have you got the preservation of the soft parts as well,” says David Briggs, a paleontologist at Yale University and member of the team.

Some researchers question the Cylindroleberididae classification, suggesting the new species belongs in a now-extinct family. “Regardless, it’s so similar to a modern form that it represents a very slow form of evolution,” responds Briggs.

One explanation for this evolutionary stability is the organism was simply well suited to its environment, he suggests.

Siveter has found previous record-holding penises. A 100 million-year-old ostracod boasting two penises found in Brazil and analysed by Siveter in 2002, held the record for oldest known members briefly. But this was usurped by another team which discovered a 400 million-year-old sex organ on a fossilized daddy-long-legs in Scotland in summer 2003.